B-Tree Node-Split.ipynb

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      "7 pivot elements:\n",
      "\n",
      " [5, 13, 16, 22, 33, 34, 41] \n",
      " [0, 1, 2, 3, 4, 5, 6, 7] \n",
      "\t|\n",
      "\t|\n",
      "\tv\n",
      "([5, 13, 16], [22], [33, 34, 41])\n",
      "([0, 1, 2, 3], [4, 5, 6, 7])\n",
      "\n",
      "\n",
      "6 pivot elements:\n",
      "\n",
      " [6, 7, 23, 29, 30, 41] \n",
      " [0, 1, 2, 3, 4, 5, 6] \n",
      "\t|\n",
      "\t|\n",
      "\tv\n",
      "([6, 7, 23], [29], [30, 41])\n",
      "([0, 1, 2, 3], [4, 5, 6])\n",
      "\n",
      "\n",
      "5 pivot elements:\n",
      "\n",
      " [0, 7, 22, 36, 41] \n",
      " [0, 1, 2, 3, 4, 5] \n",
      "\t|\n",
      "\t|\n",
      "\tv\n",
      "([0, 7], [22], [36, 41])\n",
      "([0, 1, 2], [3, 4, 5])\n",
      "\n",
      "\n",
      "4 pivot elements:\n",
      "\n",
      " [14, 15, 23, 34] \n",
      " [0, 1, 2, 3, 4] \n",
      "\t|\n",
      "\t|\n",
      "\tv\n",
      "([14, 15], [23], [34])\n",
      "([0, 1, 2], [3, 4])\n",
      "\n",
      "\n",
      "3 pivot elements:\n",
      "\n",
      " [6, 26, 39] \n",
      " [0, 1, 2, 3] \n",
      "\t|\n",
      "\t|\n",
      "\tv\n",
      "([6], [26], [39])\n",
      "([0, 1], [2, 3])\n",
      "\n",
      "\n",
      "Warning: this will create an empty leaf!\n",
      "2 pivot elements:\n",
      "\n",
      " [17, 29] \n",
      " [0, 1, 2] \n",
      "\t|\n",
      "\t|\n",
      "\tv\n",
      "([17], [29], [])\n",
      "([0, 1], [2])\n",
      "\n",
      "\n",
      "Warning: this will create an empty leaf!\n",
      "1 pivot elements:\n",
      "\n",
      " [23] \n",
      " [0, 1] \n",
      "\t|\n",
      "\t|\n",
      "\tv\n",
      "([], [23], [])\n",
      "([0], [1])\n",
      "\n",
      "\n"
     ]
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   "source": [
    "import random as rnd\n",
    "\n",
    "def random_keys(n):\n",
    "    keys = [rnd.randint(0,42) for i in range(n)]\n",
    "    keys.sort()\n",
    "    return keys\n",
    "\n",
    "# simulates a b-tree node split:\n",
    "def node_split(keys, pointers):\n",
    "    if len(keys) <= 0:\n",
    "        raise ValueError(\"keys array must contain at least one element!\")\n",
    "    if len(keys) < 3:\n",
    "        print (\"Warning: this will create an empty leaf!\")\n",
    "    pivot_position = len(keys)//2\n",
    "    pivot = [keys[pivot_position]]\n",
    "    \n",
    "    return keys[:pivot_position], pivot, keys[pivot_position+1:],  \\\n",
    "        pointers[:pivot_position+1], pointers[pivot_position+1:],\n",
    "            \n",
    "\n",
    "for n in range(7,0,-1):\n",
    "    keys = random_keys(n)\n",
    "    pointers = list(range(n+1))\n",
    "    ret = node_split(keys, pointers)\n",
    "    print(str(n)+\" pivot elements:\\n\\n\", keys,\"\\n\", pointers, \"\\n\\t|\\n\\t|\\n\\tv\", )\n",
    "    print(ret[:3])\n",
    "    print(ret[3:])\n",
    "    print(\"\\n\")\n",
    "\n",
    "#print(\"Example from the slides:\")\n",
    "#slide_example = [25, 27, 32, 45, 46, 47]\n",
    "#print(str(n)+\":\\t\", slide_example, \" ---> \", node_split(slide_example))\n",
    "#print()"
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